Field of the Invention
The present invention relates to a touch screen.
Description of the Background Art
A touch panel is a device for detecting a touch operation through an indicator such as a finger and specifying position coordinates of a touched position in the touch panel, and is noted as one of excellent user interface means. At present, touch panels of various types such as a resistive type and a capacitive type are made into products. In general, a touch panel includes a touch screen with a built-in a touch sensor (a sensor for detecting a user's touch operation), and a detecting device for specifying position coordinates of a position in which a touch is made based on a signal input from the touch screen.
As one of the capacitive type touch panels, there is a projected capacitive type touch panel (for example, see Japanese Patent Application Laid-Open No. 2012-103761). The projected capacitive type touch panel described in Japanese Patent Application Laid-Open No. 2012-103761 can detect a touch operation even if a front surface of a touch screen with a built-in touch sensor is covered with a protective plate such as a glass plate having a thickness of approximately several millimeters. The projected capacitive type touch panel is advantageously robust because the protective plate can be disposed on the front surface of the touch screen. Also in the case where a user touches the touch screen with gloves worn, moreover, the touch operation can be detected. Furthermore, the projected capacitive type touch panel has no moving unit, and thus no failure or the like caused by a movable operation of the moving unit. For this reason, a longer life can be achieved.
The projected capacitive type touch panel includes, as detection wires for detecting an electrostatic capacitance, a first series of conductive element formed on a thin dielectric film and a second series of conductive element formed above the first series of conductive element via an insulating film, for example (see Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 9-511086 (1997), for example). Each of the conductor elements forms a plurality of intersection points without any electrical contact therebetween. With the configuration described in Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 9-511086 (1997), a detection circuit detects an electrostatic capacitance formed between an indicator such as a finger and the first series of conductive element and the second series of conductive element that are the detection wires so that position coordinates of a position touched by the indicator are specified. A method of detecting the position coordinates is generally referred to as a self-capacitance detection method.
Moreover, there is a detection method for specifying position coordinates of a touched position by detecting an electric field change between a plurality of row wires extending in a row direction and configuring a first electrode and a plurality of column wires extending in a column direction and configuring a second electrode, that is, a change in a mutual capacitance (for example, see Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2003-526831). The detection method is generally referred to as a mutual capacitance detection method.
In both cases of the self-capacitance detection method and the mutual capacitance detection method, there is generally employed a method of, when a plane region (a detection cell) divided like a grid by the row wires and the column wires is touched with an indicator such as a finger, specifying position coordinates of a touched position based on balance between a detection value in the touched detection cell (sensor block) and a detection value in a detection cell in the vicinity of the sensor block.
In order to enlarge a size of a touch panel and to increase a speed, recently, touch panels have been increased which is configured by using a fine wire-shaped electrode utilizing a metallic material having a low resistance instead of a transparent conductive film such as Indium Tin Oxide (ITO) utilized so far. In a liquid crystal module provided with the touch panel using the fine wire-shaped electrode, it is necessary to suppress moire caused by an interference of a fine wire-shaped electrode pattern and a black matrix (BM) pattern formed on a color filter (CF) substrate. For example, there is conventionally disclosed the technique for suppressing moire by forming a fine wire-shaped electrode such that a fine wire-shaped electrode pattern overlaps with a black matrix pattern in planar view (for example, see Japanese Patent Application Laid-Open No. 2009-259063).
In Japanese Patent Application Laid-Open No. 2009-259063, the fine wire-shaped electrode pattern is formed to overlap with the black matrix pattern in planar view at an interval which is three times as great as a pitch in a lateral direction of a sub-pixel. With such a configuration, the black matrix and the fine wire-shaped electrode are seen with a shift depending on a viewing angle. Therefore, there are seen transmitted light from a sub-pixel having a transmittance reduced by the fine wire-shaped electrode and transmitted light from a sub-pixel having no transmittance reduced by the fine wire-shaped electrode. Accordingly, there is a problem in that a gradation of R, G and B is unbalanced, resulting in occurrence of color unevenness. In order to eliminate the color unevenness, it is sufficient to form a wire pattern with an inclination in a 45-degree direction. However, in some cases in which a touch screen is attached to an inside of a polarizing plate disposed on a display surface of a liquid crystal panel (LCD) as in an ON cell touch panel, for example, a polarizing direction of light converted through a polarizing plate disposed on a back side of the liquid crystal panel from a back light is changed in an unexpected direction by a fine wire-shaped electrode formed on a glass substrate for a touch screen. In these cases, there is a problem in that a luminous part is generated in black display, resulting in a reduction in a contrast ratio.